24. Implications of Subcutaneous Emphysema and How to Avoid and/or Limit Its Development

24. Implications of Subcutaneous Emphysema and How to Avoid and/or Limit Its Development

Kirk A. Ludwig, M.D.

There are two basic means of providing exposure within the abdominal cavity for laparoscopic procedures: mechanical abdominal wall elevation and pneumoperitoneum. Mechanical lifting devices directly elevate the abdominal wall; however, the exposure obtained is less than ideal. Pneumoperitoneum, which is established via insufflation with some type of gas, currently provides the best exposure for laparoscopic surgery. The ideal gas for insufflation would be nontoxic, nonflammable, colorless, highly soluble in blood, readily available, and cheap. Nitrous oxide, CO

, helium, air, and argon have all been used to create and maintain pneumoperitoneum. By far the most popular exposure method for laparoscopic procedures is CO

gas. The high solubility of CO

is an advantage because accidental venous embolism poses far less of a problem than the other less soluble gases used for insufflation; however, it is also a disadvantage because the readily absorbed CO

causes hypercarbia, acidosis, and other physiologic alterations. In addition to physiologic side effects, insufflation of gas into the abdomen through the abdominal wall can, on occasion, be associated with other complications such as pneumoperitoneum. Another such complication is subcu- taneous emphysema.

Subcutaneous emphysema develops when the gas being insufflated finds its way into the subcutaneous tissues of the abdominal wall. Thankfully, this is gen- erally not a very dangerous complication; however, subcutaneous emphysema at times may threaten the laparoscopic completion of the case. Therefore, it behooves the surgeon to be aware of this complication and to be familiar with methods of dealing with this problem.

A. Incidence of Subcutaneous Emphysema

It is difficult to gather precise data about this complication for several

reasons. The extent of the subcutaneous emphysema varies widely from case to

case. It may be confined to a small portion of the abdominal wall immediately

surrounding a port or extend down into the scrotum and thighs, along the flanks

to the back, and up the chest to the neck. Based on the present literature, sub-

cutaneous emphysema has been noted clinically during laparoscopy at a rate

between 0.43% and 2.3%. Well-localized subcutaneous emphysema probably

occurs more often and goes unnoticed in most cases. Because limited subcuta-

neous emphysema usually poses no problem clinically, even when detected it may not be noted in the chart. Evidence to this theory is provided by a study reporting that computed tomography (CT) scan of the upper abdomen within 24 hours of laparoscopic cholecystectomy revealed subcutaneous emphysema in 56% of patients. Long operative times (>200 minutes), the use of six or more ports, and extraperitoneal surgery (i.e., adrenal or kidney) may be risks factors for the development of this complication. In rare cases, subcutaneous emphy- sema may occur in conjunction with pneumothorax or pneumomediastinum.

B. Causes of Subcutaneous Emphysema

When a Veress needle is used to establish the pneumoperitoneum at the start of a case, it is not uncommon to misjudge the position of the needle’s tip and to inadvertently insufflate gas into the abdominal wall. This error is usually quickly recognized and corrected. This is probably the most common cause of limited subcutaneous emphysema.

There are numerous other causes or contributing risk factors. In obese patients with a very thick abdominal wall, the port may not reach far enough into the abdominal cavity so that the insufflation hole is actually not in the abdomen. In patients of normal girth, the port may be inadvertently or inten- tionally pulled back such that the insufflation hole is in the abdominal wall.

Torquing of the port in opposing directions during a case may widen the peri- toneal defect such that gas more easily tracks into the abdominal wall from the peritoneal cavity. When the “cut-down” method is used for placement of the initial port, an overly large fascial incision encourages desufflation via the port wound, which allows gas to track into the abdominal wall. Repeated dislodge- ment and reinsertion of the port may enlarge the port wound or result in new tissue paths through the abdominal wall, which makes the development of sub- cutaneous emphysema more likely. The pneumoperitoneum pressure also plays a role. The higher the pressure setting, the greater the tendency toward the devel- opment of subcutaneous emphysema. A faulty pressure gauge on an insufflator may lead to the inadvertent and unwitting use of very high insufflation pressures.

As subcutaneous emphysema develops, the abdominal wall thickness or girth increases as a result of gas dissecting into the subcutaneous tissue planes. This, in turn, shortens the length of the port that extends into the peritoneal cavity beyond the parietal peritoneal level. At a certain point the tip of the port is just barely inside the abdomen; making it more and more difficult to insufflate the peritoneal cavity without also pushing additional gas into the abdominal wall. A

“vicious cycle” results wherein the development of the emphysema increases the likelihood that further abdominal wall insufflation will occur. This added insuf- flation further increases the wall girth, and so on and so on. When this occurs it can become very difficult to complete the operation laparoscopically.

Subcutaneous emphysema can also develop when CO

traverses the

diaphragm into the mediastinum and results in a pneumomediastinum. From this

location the gas can further dissect into the subcutaneous tissue planes of the

head, neck, and chest. Barotrauma from high insufflation pressures and positive

pressure ventilation can, rarely, cause a pneumoperitoneum that may track into the subcutaneous tissues causing subcutaneous emphysema.

C. Avoiding Subcutaneous Emphysema

1. Veress needle insufflation. Improper technique in inserting the Veress needle can result in extraperitoneal insufflation with resultant subcutaneous emphysema. A summary of the proper technique for insertion and use of the Veress needle in the midline follows:

A. Check the needle for patency by flushing with saline.

B. Occlude the tip of the needle and flush with saline to check for leaks.

C. Push the blunt tip of the needle against a hard surface to be certain that it retracts and springs back into position easily.

D. Pass the needle, grasped by the shaft, via a stab incision, using the dominant hand at a 45°–90° angle to the abdominal wall with the patient in slight Trendelenburg position. Following the initial resistance, there will be two “gives” or “pops” as the needle tra- verses the linea alba fascia and then the peritoneum. Proper posi- tioning in the peritoneal cavity is confirmed by:

1) Aspiration to assess for return of blood, urine, or bowel con- tents.

2) Instillation of a small amount of saline into the needle to determine if there is free flow into the peritoneal cavity.

3) Repeated aspiration to be sure that none of the saline is recoverable (saline return indicates that the needle tip is in a hollow organ or other closed space).

4) Closure of the stopcock on the needle, filling the hub with saline, elevating the abdominal wall, then opening the stop- cock to confirm that the saline flows rapidly into the abdom- inal cavity [the so-called drop test].

5) Advancement of the needle a short distance further without encountering any resistance.

Only after confirming proper placement of the needle is insufflation begun. Initial insufflation pressure of greater than 10 mmHg indicates a problem, one of which may be extraperitoneal insufflation. Insufflation is begun at a low flow and increased after 1–2 L CO

has been insufflated. If a problem is encountered, stop insufflation, withdraw the needle, and then start over again.

2. Open “cut-down” method. An alternative method for establishing pneu- moperitoneum is the “open” technique using a Hasson cannula. A small incision is made at the umbilicus, or an alternate site, and the incision is carried down to the fascia. A small incision is made in the fascia, only large enough to accept an index finger, and the underlying peritoneum is grasped, elevated, and incised.

Traction sutures, placed through the peritoneum and fascia, are placed on either

side of the fascial incision. Next, the blunt trocar is inserted into the abdominal

cavity and its position secured by wrapping each end of the fascial suture around the wings of the cone-shaped tip of the Hasson cannula. The open technique of insufflation is probably safer than the closed technique and, when executed prop- erly, pneumoperitoneum is established just as rapidly, if not more rapidly, than with the closed technique. Development of subcutaneous emphysema with this technique should be a rare occurrence. Keys to avoiding extraperitoneal insuf- flation are:

A. Keep the skin and fascial incisions small.

B. If possible, place the traction sutures through the peritoneum and the fascia, not just the fascia.

C. Make sure the blunt-tipped trocar is positioned within the peri- toneal cavity.

D. Using strong upward pressure on the traction sutures, advance the cone-tipped end of the Hasson cannula into the fascial opening as far and as tight as possible before securing to the wings. High pressures may be noted if insufflation is attempted when the cannula is improperly positioned in the extraperitoneal space.

3. Faulty insufflator. A faulty pressure/flow shutoff mechanism can result in dangerously high intraabdominal pressure and resultant subcutaneous em- physema. The proper function of the insufflator can be checked easily. To assure proper function:

A. Turn the insufflator to high flow (>6 L/min) with the tubing not yet connected to a cannula or Veress needle; the intraabdominal pressure indicator should be 0.

B. Lower the flow to 1 L/min and occlude the tubing. The pressure reading should go to 30 mmHg and the flow indicator should go to 0.

4. Insufflation pressure. For most laparoscopic procedures, the pressure limit should be set at 12–15 mmHg. Intraabdominal pressures higher than this can be problematic and contribute to the formation of subcutaneous emphysema as CO

is insufflated under high pressures around cannulas.

5. Number of ports. Subcutaneous emphysema can result from leakage around any port; the more ports that are utilized the greater the incidence. There- fore, the minimum number of ports that will permit safe completion of the case should be placed.

6. Angle of port insertion. The manner in which the cannulas are placed has a bearing on the chances that subcutaneous emphysema may develop. Each cannula should be placed so that its axis is at an appropriate angle for the case at hand. In placing ports, this should be kept in mind, especially in patients with a thick abdominal wall. The cannula should enter the peritoneal cavity at an angle such that there will be minimal movement of the cannula within the abdominal wall during the procedure (generally angled toward the quadrant where the pro- cedure is to be done). If the port is angled toward the head and there is lower abdominal or pelvic dissection to be done, then it will be necessary to torque the port in the opposite direction, which will likely tear and enlarge both the peritoneal defect and the abdominal wall wound.

In patients with a thick abdominal wall in whom the port is placed at

an angle, there will be a significant difference between the location of the

incision on the skin and the point at which the cannula enters the peritoneum.

The surgeon should take this fact into account when choosing the port sites.

7. Port anchoring. Particularly during long cases, port dislodgement or port slippage may occur, which increases the chances of subcutaneous emphysema developing. Therefore, it is advisable to anchor all ports to the abdominal wall to prevent complete dislodgement and to stabilize each port’s position in regard to the length of the cannula within the abdominal cavity to prevent slippage.

Threaded ports that are “screwed” into the abdominal wall anchor them- selves. Most such ports are reusable. An accessory port anchor or grip of some type is available for most nonthreaded disposable ports. Most such grips are threaded and cone shaped (Christmas tree shaped); the port is inserted through the center of the grip with the narrow end of the grip oriented toward the port tip. Once the proximal end of the port has been inserted into the abdomen, the port anchor is screwed into the abdominal wall. The grip prevents the port from being dislodged and also prevents slippage of the port. The length of the port within the abdomen can be altered, usually by pinching a valve on the grip, which allows movement of the port within the grip.

Regardless of whether a threaded port or port grip is used to anchor the port, it is advisable to further secure the port via a skin stitch placed adjacent to the cannula. A “0”-gauge suture is ideal for this purpose. The suture is loosely tied down to the skin after being placed. One end of the suture is then wrapped around the insufflation arm of the port several times, after which it is pulled down toward the abdominal wall. The opposite end of the suture is then pulled upward and the two lengths of the suture are clamped together. This prevents port dislodge- ment in the rare instance, usually late in the case, when the port grip or the threaded port fails to anchor the cannula. If this type of anchoring suture is used, it is necessary to unclamp the suture to alter the length of the port in the abdomen. After adjusting the port position, the two ends of the suture are again clamped together after one of them has been wrapped about the insufflation arm.

8. Means of limiting the expansion of the abdominal wall’s girth after subcutaneous emphysema has developed. As mentioned, once the problem has been noted, the expanding abdominal wall makes it increasingly difficult to keep the port tip in the abdomen. The following method stabilizes abdominal wall girth near a port and requires only large nylon sutures on “retention suture”-type needles. With the laparoscope observing the port to be anchored, a #2 nylon on the largest available curved needle (which is straightened out before being inserted) is passed through the entire abdominal wall adjacent to the port in ques- tion. A laparoscopic needle driver or other grasper is used to grasp the shaft of the needle once it has entered the abdomen. The needle is then carefully pulled into the abdomen and then turned 180° so that the sharp tip is facing the under- side of the abdominal wall. As the needle is being pulled into the abdomen, the tip is kept in full view via the laparoscope so that no injuries are made. As the needle is turned around, the heel of the needle is followed rather than the tip, because the heel is now adjacent to the bowel rather than the tip of the needle.

The needle is then driven back through the abdominal wall adjacent to the port

but some distance away from the entry site. The needle is then pulled back out

through the abdominal wall to the outside. In obese patients the needle may not

project through the skin, which necessitates careful compression of the abdom-

inal wall to find it. One end of the suture is then wrapped around the insuffla-

tion armature three or four times and then pulled down toward the abdominal wall while the opposing end of the suture is pulled upward alongside the port.

An assistant then clamps the two strands together, which serves to compress the abdominal wall and drive the port into the abdomen. This method compresses the abdominal wall and keeps the tip of the port within the abdomen. This method is useful in any instance where the port will not stay in the abdomen.

This method works best in conjunction with a port grip but can be used without one if necessary. The grip prevents the external part of the port shaft from being pushed fully into the abdomen by the transabdominal wall nylon suture when it is tightened around the insufflation arm.

D. Recognition of Subcutaneous Emphysema

1. Crepitus. Subcutaneous emphysema can appear early during laparoscopy, but it more typically presents 45–60 minutes after commencement of pneumoperitoneum. When it is limited, it often goes unnoticed until the end of the operation, hidden from the surgeon’s view by the drapes as it extends downward into the groin and scrotum or upward into the chest, neck, and head.

At that point this complication is usually noted by pushing down on the skin in the affected area, which reveals crepitus. The extent of the crepitus reflects the limits of the subcutaneous emphysema.

2. Insufflation problems. More extensive subcutaneous emphysema may be first noted during the case when maintenance of a sufficient pneumoperi- toneum becomes difficult due to an expanding abdominal wall and numerous CO

leaks. Examination of the abdominal wall and port sites in this case will reveal crepitus. Placement of the transabdominal full-thickness nylon sutures to compress the abdominal wall and to maximize the length of the port in the peri- toneal cavity as described in the above section (Section C.8) usually improves the situation.

3. Hypercarbia and acidosis. CO

is readily absorbed from the subcuta- neous space; in some cases this absorption will result in notable physiologic changes. When this occurs, the first clinical sign may be a sudden and brisk increase in the end tidal CO

, which should be detected by the anesthesiologist.

At this point, a marked increase in PaCO

and a systemic acidosis may be noted on blood gas. What determines whether significant physiologic alterations develop is the extent of the subcutaneous emphysema and the ability of the patient to clear the additional CO

via the lungs.

4. Pneumoperitoneum-related pneumothorax. In laparoscopic cases

where a pneumothorax develops secondary to gas escaping through the

diaphragm into the chest, the anesthesiologist may recognize an increase in

airway pressure or a decrease in lung compliance. The associated hypercarbia

and acidosis can lead to cardiac arrhythmias (particularly ventricular), sinus

tachycardia, and hypertension. An examination of the patient for subcutaneous

emphysema and auscultation of the chest for breath sounds should be carried

out if the pulmonary end-tidal CO

increases substantially during a laparoscopic

case. A portable chest X-ray will demonstrate a pneumothorax, which can be

managed via needle decompression of the hemithorax followed by placement of an anterior chest tube, if needed. Tension pneumothorax, with its attendant hemodynamic effects, is managed directly without a chest X-ray by immediate decompression. The surgeon should also remember that pneumothorax can develop from rupture of a pulmonary bleb and thus, in this case, not be related to the pneumoperitoneum at all.

5. Pneumoperitoneum-related pneumomediastinum. Insufflated CO

can also track from the abdominal cavity into the mediastinum and result in a pneu- momediastinum. This can occur at congenital weak points or defects in the diaphragm, or it can occur when tissue planes along the vena cava, aorta, or retroperitoneum are disturbed, thus providing a pathway to the mediastinum for the gas. Most cases of pneumomediastinum associated with laparoscopy resolve spontaneously with observation and without major intervention. However, lifethreatening complications can occur if insufflation is continued once the pneu- momediastinum has developed. Pneumopericardium in association with pneu- momediastinum and subcutaneous emphysema has, very rarely, been reported and may be associated with potentially life-threatening cardiac tamponade.

E. Management of Subcutaneous Emphysema

1. When noted during the case. The patient should be quickly evaluated for the presence of a pneumothorax via auscultation of the lungs and, if neces- sary, by obtaining a chest radiograph. The patient’s pulmonary end-tidal CO

and arterial CO

levels should be checked and, if high, the minute ventilation and inspiratory pressure adjusted to lower the PETCO

and PaCO

to acceptable levels. The anesthesiologist should also discontinue the use of nitrous oxide because it rapidly enters the space containing the CO

, adding to the gas volume in the subcutaneous tissues. The insufflation pressure should be reduced to as low a level as possible to maintain adequate exposure and the operation com- pleted promptly. If expanding abdominal wall girth and maintenance of an ade- quate pneumoperitoneum is a problem, then full-thickness nylon sutures should be placed adjacent to the ports and used as described in Section C above to com- press the abdominal wall and keep the port tip in the abdomen. Obviously, if it is not possible to sufficiently lower the PaCO

levels via manipulation of the res- pirator settings, or it is not possible to maintain adequate laparoscopic exposure, then conversion to an open procedure will be necessary.

2. When noted at the end of the case. The patient should be evaluated for pneumothorax and the PETCO

and PaCO

levels assessed as described above.

Before extubation, it is crucial that the end-tidal and arterial CO

levels be within

normal limits. In patients with severe chronic obstructive pulmonary disease or

those with ventilatory dysfunction due to medications (opioids or anesthetic

medications), mechanical ventilation may need to be continued postoperatively

until the CO

levels normalize. If the subcutaneous emphysema involves the

chest and neck then, before extubation, the upper airway is carefully evaluated

to be sure there is no airway compression. It is important to reassure the patient

that the subcutaneous emphysema will resolve spontaneously over a relatively

short period of time.

F. Selected References

Abe H, Bandai Y, Ohtomo Y, et al. Extensive subcutaneous emphysema and hypercapnia during laparoscopic cholecystectomy: two case reports. Surg Laparosc Endosc 1995;

5:183–187.

Hasel R, Arora SK, Hickey DR. Intraoperative complications of laparoscopic cholecys- tectomy. Can J Anaesth 1993;40:459–464.

Holzman M, Sharp K, Richards W. Hypercarbia during carbon dioxide gas insufflation for therapeutic laparoscopy: a note of caution. Surg Laparosc Endosc 1992;2:11–14.

Kent RB. Subcutaneous emphysema and hypercarbia following laparoscopic cholecystec- tomy. Arch Surg 1991;126:1154–1156.

Klopfenstein CF, Gaggero G, Mamie C, et al. Laparoscopic extraperitoneal inguinal hernia repair complicated by subcutaneous emphysema. Can J Anaesth 1995;42:523–525.

Pearce DJ. Respiratory acidosis and subcutaneous emphysema during laparoscopic chole- cystectomy. Can J Anaesth 1994;41:314–316.

Richard HM, Stancato-Pasik A, Salky BA, et al. Pneumothorax and pneumomediastinum after laparoscopic surgery. Clin Imaging 1997;21:337–339.

Rudston-Brown BCD, MacLennan D, Warriner CB, et al. Effect of subcutaneous carbon dioxide insufflation on arterial pCO

. Am J Surg 1996;171:460–463.

Wahba RWM, Tessler MJ, Kleiman SJ. Acute ventilatory complications during laparo- scopic upper abdominal surgery. Can J Anaesth 1996;43:77–83.

Wolf JS, Clayman RV, Monk TG, et al. Carbon dioxide absorption during laparoscopic

pelvic operation. J Am Coll Surg 1995;180:555–560.